The association between blood clot formation, inflammation and cancer is strong. Cancer predisposes patients to the development of blood clots, which may complicate therapy and has a higher risk of morbidity and death than in non-cancer patients. The converse is also true, nearly 50% of patients who develop unprovoked venothromboembolic disease (VTE) harbor an occult cancer, yet a search for cancer in these patients is not considered standard of practice. The diagnosis of blood clot formation is compromised when the clot is in the abdomen or pelvis, and/or the patient has a containdication to iodinated contrast. In cancer patients, multiple anatomic abnormalities associated with the cancer or its treatment, and a heightened propensity for intraabdominal or pelvic clot may further complicate the diagnosis of VTE. Further, no current methods exist to identify patients at particularly high risk for cancer-related thrombosis, a critical step in thrombo-prevention. The link between clot, cancer and inflammation may be due to a host response to cancer resulting in expression of both local and systemic inflammatory cytokines and tissue factors that act on platelets and myeloid leukocytes to produce a cascade of events culminating in blood clot formation. FDG PET imaging has emerged as a powerful tool in the diagnosis, staging, and therapeutic assessment of malignancy. Based on preliminary data and personal observation, we hypothesize that FDG PET may be a useful adjunct in the diagnosis of complicated cases of VTE, in identifying patients with unprovoked VTE that harbor an occult malignancy, and in identifying the systemic state that predisposes many cancer patients to VTE. The specific aims of this project will test these hypotheses in human subjects and also span from benchtop to bedside. In vitro studies complete the molecular imaging loop, by characterizing the relationship between FDG uptake, activation of prothrombotic cells, and expression of known prothrombotic gene products and effectors by these cells.